With the continued popularity of top-rope climbing and rock gyms, there has been a need for self-belaying devices in the absence of suitable climbing partners for belaying the climber. Such devices would also be of value for top-rope activities where the rock is known to be unstable, thereby presenting significant danger to belayers.
Rope clamping devices which move substantially freely along a rope when it is not under significant tension are known. For example, U.S. Pat. No. 3,967,349 for "Clamp For Flexible Rope," which issued to Donald E. Christensen on Jul. 6, 1976, describes a self-tightening clamp assembly which may slide along a rope as long as the rope is flexible, but clamps onto the rope when the rope becomes taut, thereby reversibly securing the clamp along the rope. The self-tightening clamp assembly includes a clamp body having a longitudinal opening extending through it from end to end, for receiving a portion of a flexible rope so that the rope extends forward and rearward of the clamp assembly. Within the clamp body is a clamp surface that extends longitudinally along one side of the opening for engaging the rope. A clamp plate is movably mounted to the clamp body on an opposite side of the opening for engaging the rope and clamping it against the clamp surface. Lever means are provided, pivotably mounted to the clamp body, with one end operatively connected to the clamp plate and with a remaining end projecting rearwardly from the clamp body. The lever means functions to move the clamp plate toward the clamp surface in response to pivotal movement of the remaining lever end. Connecting means are also provided for releasably securing the remaining lever end to he flexible rope so that, as the rope is drawn to a taut condition between ends, the lever is automatically operated to force the clamp plate toward the clamp surface, thereby clamping the rope therebetween. In addition, as the rope slackens, the lever is automatically operated in response thereto to relax clamping pressure against the rope. As designed, the device requires that the rope be threaded through the opening in the clamp body, and that the rearward end of the rope flex sufficiently when not taut, in order or the clamp assembly to release. Additionally, if used in a climbing environment, a fall could easily occur which would not cause the rearward end of the rope to become taut, thereby causing the device to fail to clamp the rope.
Cam cleat devices which permit a rope to move freely therethrough in one direction, while automatically engaging and stopping a rope from passing in the opposite direction are well known. For example, U.S. Pat. No. 4,716,630 for "Cam Lock With Positive Release" which issued to Helmut K. Skyba on Jan. 5, 1988, and U.S. Pat. No. 4,217,847 for "Self-Release Cam Cleat" which issued to Robert A. McCloud on Aug. 19, 1980, describe such devices. Devices employing such camming apparatus are currently marketed for use in climbing as ascenders. However, once a fall has occurred, the rope is jammed so tightly by the cams that all weight must be removed from the rope in order to release it. That is, the climber must climb above the jammed ascender.
A device specifically designed for climbing is described in U.S. Pat. No. 5,076,400 for "Self-Jamming Safety Device For A Rope," which issued to Paul Petzl and Pierre Petzl on Dec. 31, 1991, where an internal cam locks in place under sudden force to prevent the rope from feeding out further. The device, which also can be used for rapelling, includes two pulleys, one of which is fixed on a base flange, and the other on a support plate capable of pivoting on an articulation spindle. The first pulley is provided with a first braking surface, against which the rope is pressed by a boss of the pulley when the support plate is driven by the tension in the rope to a first jamming position. The pulley is equipped with a second braking surface operating in conjunction with the first surface following continued pivoting movement of the support plate to a second jamming position. Switching between the two jamming positions takes place after the tension of the rope has exceeded a preset threshold. It should be pointed out that the rope is configured in an S-shape by the device, thereby adding significant resistance to motion of the rope therethrough while the user is climbing.
Both of the latter devices described hereinabove specify the use of pivoted members.
Accordingly, it is an object of the present invention to provide a climbing rope safety apparatus which automatically clamps the rope when a fall occurs.
Another object of the invention is to provide a climbing rope safety apparatus which automatically clamps the rope when a fall occurs, and which can be used as a descender.
Yet another object of the present invention is to provide a climbing rope safety apparatus which automatically clamps the rope when a fall occurs, but generates little resistance to the passage of the rope therethrough while the user is climbing in an upward direction.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.